PROJECT SUMMARY Gestational diabetes (GDM) is a common complication of pregnancy with substantial disparities between racial/ethnic and immigrant groups. diabetes on contribute Women with GDM are at an increased risk of later developing Type 2 (T2DM), and data on disparities in T2DM following GDM suggest the greatest effect of GDM the transition to T2DM in black and Hispanic women. Thus GDM disparities are critical because they could to lifecourse T2DM disparities. limited GDM has the potential to be an early warning system for T2DM and therefore is an opportunity to intervene to reduce T2DM disparities in women. Unfortunately, this opportunity is often missed due to inadequate long-term follow-up. Glycosylated hemoglobin (HbA1C) is a well-established diagnostic tool for T2DM, with recommended guidelines for diagnosis and control of T2DM. However, data is scarce about prevalence and predictors of long-term HbA1c screening following GDM, and population-based measures of HbA1c levels during and beyond pregnancy. Further, influence of race/ethnicity and nativity on these measures has not been adequately investigated. A major barrier to filling this gap is the lack of a large, diverse GDM cohort with valid outcome measures. We propose a secondary data analysis using linked birth certificate, hospital discharge, and HbA1c registry data from the years 2009-2017 to construct a population- based retrospective cohort. In this novel pregnancy cohort, we aim to: 1) Characterize HbA1c profiles prenatally and through eight years postpartum in women with and without gestational diabetes, overall and by race/ethnicity/nativity; 2) Among women with a GDM pregnancy, determine racial/ethnic/nativity and socioeconomic disparities in long-term HbA1c testing up to eight years postpartum; 3) Among women with a GDM pregnancy, measure racial/ethnic/nativity disparities in longitudinal T2DM outcomes (T2DM and glucose control) and examine prenatal HbA1c levels and clinical characteristics of pregnancy as predictors of poor outcomes. Discoveries of disparities in long-term screening and T2DM outcomes over 8 years of follow-up will guide future interventions to use GDM as a lever to prevent lifecourse T2DM disparities.